researchers hypothesize that "sleep paralysis" causes SUNDS, are they suggesting that the mechanism that normally paralyzes the body during REM sleep somehow goes haywire, perhaps by paralyzing the heart or lungs, and causes death? ''Clinical manifestations Sudden unexplained nocturnal death syndrome predominantly affects previously healthy, young adult Southeast Asian males, who die suddenly during sleep. Death often occurs 3 to 4 hours after sleep onset, and witnesses have observed choking, gasping, groaning, gurgling, frothing at the mouth, labored breathing without wheezing or stridor, screaming, and other signs of terror. The inability to arouse takes place, which is followed by rapid collapse and death from ventricular fibrillation. Apparent sleep terrors have been reported to occur frequently in subsequent victims of sudden unexplained nocturnal death syndrome. '' Many cases are reported to have a fixed and "terrified" expression on their face.